I should have realized you were thinking there was an in and out on the 859......It would be nice if you could "daisy chain" the Ethernet...But I don't think I have ever seen a computer or other Ethernet device that could do that.....If you have ever set up a home network, you have to have a common hub....either wired or wireless.

The other thing I would consider is making your stern unit a SI unit.....I wouldn't have a boat that wasn't set up with a LEAST on SI unit.